This invention pertains generally to electronic engine control systems and specifically to a novel electronic circuit for said systems.
The prior art contains electronic engine control circuits which utilize an integrator for providing a reference signal indicative of engine crankshaft position, the integrator being reset at predetermined engine crank angles. For an eight cylinder engine the integrator is typically reset at 90.degree. intervals. The integrator output is compared against a desired timing signal and when a predetermined relationship between the two occurs, an engine timing control signal is given. Because the desired timing signal is a function of one or more parameters useful in controlling the engine, the engine angle, or timing, of the engine timing control signal is thereby controlled in accordance with these input parameters.
The present invention is directed toward a novel engine control and novel circuitry for engine control which utilizes an integrator which is reset at predetermined engine crank angles. Attempts to adapt prior art integrators to a four cylinder engine have encountered a noticeable deterioration in accuracy. One source of this inaccuracy is the longer duration of the integrator period. For example, in going from an eight cylinder to a four cylinder system, the period of an integrator sawtooth waveform increases from 90.degree. to 180.degree.. In a closed-loop type system (for example as shown in U.S. Pat. No. 3,885,534 assigned to the same assignee as the present application) inaccuracies are observed particularly under transient conditions because of associated time constants. Such problems are accentuated in a four cylinder engine because of its more dynamic response.
The present invention provides an improvement whereby these inaccuracies are greatly attenuated or even eliminated entirely thereby promoting accuracy in the timing function. While the present invention is particularly well suited for a four cylinder engine, it will be appreciated that the principles disclosed herein may be applied to other engine configurations.